Method and apparatus for cleaning a processing tube

ABSTRACT

A method for cleaning a processing tube is performed by an apparatus providing a vacuum and a flow of an inert gas. The flow of the inert gas dislodges particles from the tube surface and assists in carrying the particles to the vacuum. The vacuum is centered in the tube, thus preventing the sides of the tube from being scraped. Wheels are attached to the vacuum means to facilitate cleaning of the tube.

BACKGROUND OF THE INVENTION

This invention relates to, in general, the cleaning of processing tubes,and more particularly, but not limited to, the removal of particles froma processing tube used for semiconductor processing.

In semiconductor wafer processing, the wafers are processed in a furnacewhich is in the shape of a cylindrical tube made of quartz. It isimportant that these be substantially free of any particles which can bedeposited on semiconductor wafers which are processed therein. Particlesdeposited on the wafers can result in defects formed in thesemiconductor device.

Therefore, in situ cleaning is performed periodically on the tube to tryto remove loose particles present in the tube. After in situ cleaning,tests must then be performed on the tube to ensure that the number ofparticles present in the tube are below a minimum level. This testentails inserting dummy wafers which have a known quantity of particlesthereon, running a temperature cycle, and then remeasuring the amount ofparticles on the wafer. If the particle count has gone up by a certainamount, the tube must then be cleaned, in situ, before a production runmay start.

In the past, in situ cleaning involved using a vacuum wand having atriangular shaped head on one end (similar to a standard attachment fora vacuum cleaner used in the home). The vacuum pull was from the bottomof the head. The vacuum wand was inserted into the tube to vacuum anyloose particles which had fallen to the bottom portion of the tube.

One of the problems with this method was that the vacuum head oftenscraped the sides of the tube which created more particles to beremoved. These additional particles were created by scratching of thetube itself or by scraping of a film deposited on the tube. The scrapingof the film caused the film to flake and create more particles.

In addition, the vacuum head focused the vacuum only in a lower quadrantof the tube, therefore, only loose particles which fell to the bottom orwhich could be dislodged by the vacuum were removed. Particles whichwere lodged in other quadrants of the tube were not removed by thevacuum. However, these particles could be dislodged during theprocessing of semiconductor wafers, resulting in defects formed on thesemiconductor devices formed on the wafers. Basically, this crude methodof removing particles was ineffective and needed much improvement.

If in situ cleaning fails to provide a certain level of cleanliness inthe tube, it must be removed from a furnace bank and chemically cleaned.The process of removing the tube from the furnace bank is cumbersome andtime consuming. The tube must first be cooled down from an operatingtemperature of approximately 400° C. before removal. A new tube must beinserted and brought up to operating temperature. It would be desirableto have a more effective in situ clean in order to reduce the amount oftimes the tubes must be changed.

SUMMARY OF THE INVENTION

An apparatus and method for cleaning a tube is accomplished by a vacuummeans coupled to a flow of a gas. The vacuum means is coupled to a meansfor supporting the vacuum means against a surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a partial cross sectional view and a partial sideview of an embodiment of an apparatus of the present invention;

FIG. 2 illustrates a perspective view of a portion of an embodiment ofan apparatus of the present invention; and

FIG. 3 illustrates a frontal view of a portion of an embodiment of anapparatus of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the present invention. What is shownis an apparatus comprised of a means for distributing a vacuum orconduit 10 having a first end 11 and a second end 12. First end 11 isadapted to receive a vacuum head 13 having a substantially circular face15 and at least one vacuum channel 16 formed preferably at the perimeterof face 15. By forming vacuum channel 16 at the perimeter, the vacuumcan be focused substantially at the perimeter of a tube, at walls 38 ofa processing tube 37 (shown in FIG. 2), to provide for more efficientremoval of the particles which will be dislodged from walls 38. Theamount of vacuum necessary should be enough to effectively removeparticles present in the tube. It was found that 20-30 inches of mercurywas adequate to remove particles found in semiconductor processing.Vacuum channel 16 communicates with conduit 10. Vacuum head 13 ispreferably removably coupled to conduit 10 at first end 11.

It is desirable that vacuum head 13 have a diameter which closely fitsthe diameter of diffusion tube 37 to be cleaned, to more efficientlyremove particles from tube 37. Therefore, in a preferred embodiment,face 15 of vacuum head 13 has a diameter which closely fits the diameterof the tube to be cleaned. It was found that a diameter one-half inchless than the diameter of tube 37 was adequate for particle removal andprevention of scraping the sides of tube 37. Scraping the sides of thetube can cause scratching of the tube which creates more unnecessaryparticles or scratching of the film deposited on the diffusion tubewhich causes flaking and the creation of more particles.

At second end 12, vacuum connection or hose 18 is preferably removablycoupled to conduit 10. A vacuum means 20 is coupled to vacuum hose 18.Vacuum means 20 can be provided by, for example, a pump which provides apressure differential to cause a vacuum from vacuum head 13 to vacuummeans 20. Conduit 10 and vacuum head 13 are shown in cross section,while the remainder of the apparatus in shown in side view to betterillustrate the apparatus.

The apparatus is also comprised of a means for providing an inert gasflow adjacent vacuum head 13. An inert gas supply means 31 is coupled toa hose 29 which is coupled to a first end 25 of a conduit 24. Inert gassupply means 31 can be provided, for example, by a pump providing apressure differential to cause flow of the inert gas out of pipes 33. Ina preferred embodiment, conduit 24 is coupled to conduit 10 through aninlet hole 23 formed in conduit 10 and runs inside a portion of conduit10 and vacuum head 13.

At a second end 27 of conduit 24, a plurality of pipes 33 extendoutwardly from conduit 24. Pipes 33 are configured to provide a flow ofan inert gas 35, as shown in FIG. 2, so that the flow of inert gas 35 isdirected against walls 38 of processing tube 37. Preferably, pipes 33are configured to direct inert gas 35 toward vacuum channel 16 tofacilitate the removal of particles from tube 37. Note that in thisembodiment shown in FIG. 2, pipes 33 are straight, but directed at anangle toward vacuum head 13. FIG. 2 illustrates another configuration ofpipes 33, which are shown to be curved toward vacuum head 13. Otherconfigurations are possible, as long as inert gas flow 35 is directedtoward walls 38 and vacuum head 13, in the preferred embodiment. In apreferred embodiment, four pipes 33 are used in order to provide inertgas flow 35 in each quadrant of tube 37. Obviously, more pipes 33 wouldprovide for more efficient removal of particles. Further, in a preferredembodiment, pipes 33 should extend radially toward walls 38 of tube 37as far as vacuum head 13.

The pressure of the flow of inert gas 35 should be enough to effectivelydislodge particles present in the tube. It was found that 30-50 poundsper square inch was adequate to dislodge particles found insemiconductor processing tubes.

A first embodiment of a means for supporting conduit 10 is provided bysupport members 42 coupled to conduit 10. Rolling means or wheels 40 arecoupled to support members 42. The purpose of support members 42 andwheels 40 will be discussed with reference to FIG. 3 below.

FIG. 2 illustrates that vacuum head 13 may also be configured in asubstantially spherical configuration rather than a conicalconfiguration as shown in FIG. 1. Any configuration is possible. Vacuumchannel 16 is preferably sealed against conduit 24 (one embodiment shownin FIG. 1) in order to focus the vacuum at the perimeter of face 15 ofvacuum head 13. In this manner, particles which are dislodged from walls38 of a processing tube 37 are assisted into vacuum channel 16 by theflow of vacuum and inert gas flow 35. FIG. 1 illustrates only one way inwhich vacuum channel 16 may be sealed against conduit 24. It is alsopossible to provide a stopper or O-ring around conduit 24 abutting thewalls of conduit 24 and the walls of vacuum channel 16 to seal off theremainder of vacuum head 13 and conduit 10. Spacers 14 are used tofacilitate forming channel 16 if vacuum head 13 is formed as a conewithin a cone configuration.

It is preferable that pipes 33 can be removed from conduit 24 in orderto facilitate the changing of vacuum head 13. In one embodiment, pipes33 may be removed by removing a portion of conduit 24 along withconduits 23 at a coupling 26 provided in conduit 24.

FIG. 3 illustrates a frontal view of a portion of an embodiment of thepresent invention. A second embodiment of a means for supporting conduit10 is provided by a support member having a substantially verticalportion 43 coupled to conduit 10. Two outwardly extending portions 47 ofthe support member outwardly extend away from vertical portion 43. Apair of rolling means or wheels 40 are coupled to each portion 47 of thesupport member. Wheels 40 and the support member preferably also providefor a means for centering the apparatus within processing tube 37.Wheels 40 are preferably at an angle of approximately 120°, measuredfrom the center of conduit 10 and illustrated by line 45, in order tofacilitate centering vacuum head 13 within tube 37. The centering ofvacuum head 13 within processing tube 37 is important so that vacuumhead 13 does not scrape walls 38 of processing tube 37.

Wheels 40 are preferably comprised of ceramic or other inert materialswhich do not leave contamination on tube walls 38. The remainder of theapparatus of the present invention may be fabricated of any materialwhich can withstand temperatures of at least 400° C., such as, forexample stainless steel, ceramic, or quartz, to name a few. Theapparatus preferably should be able to withstand such temperatures sothat the tube may be cleaned in situ, while it is at idle temperature.Wheels 40 facilitate the insertion and removal of the apparatus within atube 37 and prevent scratching of tube walls.

To increase the usability of the cleaning apparatus of the presentinvention, the support member and wheels 40 should be able to retract orextend toward or away from conduit 10 in order to use and center theapparatus within tubes of a different size. This is accomplished byhaving vertical portion 43 of the support member retractable at alocation 44 and outwardly extending portions 47 retractable at locations48. A position may be held in place by a set screw 44 on the verticalportion 43 and set screws 48 on the outwardly extending portions 47, forexample. In addition, if the apparatus of the present invention isutilized in a vertical tube, rather than a horizontal tube, the meansfor centering the apparatus would preferably need to be comprised of athird wheel 40 (not shown) supported by another support member having aportion similar to vertical portion 43 in order to center the apparatuswithin a vertical tube. As stated above, vacuum head 13 is alsopreferably removably coupled to conduit 10. Thus, the apparatus of thepresent invention can be used and optimized for cleaning of various tubesizes.

Note that only two ways of supporting and/or centering the apparatus ofthe present invention in a tube has been shown. These are only two waysin which this may be done, many other ways are possible.

With reference to all of the FIGS. of the present invention, processingtube 37 is cleaned by inserting the apparatus of the present inventioninto the opening of processing tube 37. Vacuum means 20 and the flow ofinert gas 35 are turned on while the apparatus is inserted intoprocessing tube 37 and removed from processing tube 37. The flow ofinert gas 35 will dislodge any particles which are stuck to the sides ofthe processing tube 38 and assist in directing those and other looseparticles into vacuum head 13. The flow of inert gas 35 is important tofacilitate the removal of particles which are lodged into walls 38 andcannot be removed simply by vacuum means 20 alone.

It is important to note that the apparatus of the present invention doesnot remove the film which is commonly deposited on the sides of tube 37during some of the processing of semiconductor wafers. It is onlydesirable to remove particles and dust which are loose enough to bedeposited on semiconductor wafers during processing. It was found thatan insertion and removal rate of the apparatus of the present inventionof approximately two inches per second was adequate to remove theseparticles from processing tube 37.

As can be seen, an apparatus and method for cleaning processing tubes,in situ, has been provided. The apparatus of the present inventionallows for the dislodging of particles from the walls of a diffusiontube and subsequent removal thereof. In addition, the apparatus of thepresent invention minimizes the amount of scraping of the sides of adiffusion tube which creates more particles that must be removed. Theapparatus of the present invention is easy to use and the method ofusing it is not time consuming. Therefore, the removal and replacementof processing tubes for a chemical clean can be extended or minimized byusing the apparatus of the present invention.

We claim:
 1. A cleaning apparatus, comprising:a conduit having a firstend and a second end; means for providing a vacuum coupled to the firstend of the conduit; a head having a face coupled to the second end ofthe conduit, wherein the face has at least one channel formed thereinwherein the at least one channel is coupled to the vacuum means; meansfor providing a flow of a gas coupled to the head wherein the gas isdirected at an angle toward the head; and means for supporting theconduit against a surface coupled to the conduit, the supporting meansincluding a means for rolling comprised of ceramic.
 2. The apparatus ofclaim 1 wherein the head has a substantially circular face.
 3. Theapparatus of claim 2 wherein the head has a diameter which closely fitsa diameter of a tube in which the apparatus is inserted.
 4. Theapparatus of claim 2 wherein the head has a diameter of approximatelyone-half inch less than a diameter of a tube in which the apparatus isinserted.
 5. The apparatus of claim 4 wherein the rolling means arecomprised of two wheels.
 6. The apparatus of claim 1 wherein the head isremovably coupled to the conduit.
 7. The apparatus of claim 1 whereinthe supporting means is adjustable for appropriate positioning withinthe tube.
 8. The apparatus of claim 1 wherein the gas means is providedby a conduit positioned inside the head.